“The aphotic zone (aphotic from Greek prefix ἀ- + φῶς "without light") is the portion of a lake or ocean where there is little or no sunlight. It is formally defined as the depths beyond which less than 1 percent of sunlight penetrates. Above the aphotic zone is the photic zone, which consists of the euphotic zone and the disphotic zone. The euphotic zone is the layer of water in which there is enough light for net photosynthesis to occur. The disphotic zone, also known as the twilight zone, is the layer of water with enough light for predators to see but not enough for the rate of photosynthesis to be greater than the rate of respiration.”
“The depth at which less than one percent of sunlight reaches begins the aphotic zone. While most of the ocean’s biomass lives in the photic zone, the majority of the ocean’s water lies in the aphotic zone. Bioluminescence is more abundant than sunlight in this zone. Most food in this zone comes from dead organisms sinking to the bottom of the lake or ocean from overlying waters.”
“Unusual and unique creatures dwell in this expanse of pitch black water, such as the gulper eel, the giant squid, the anglerfish, and the vampire squid. Some life in the aphotic zone does not rely on sunlight at all. Benthic communities around methane seeps rely on methane-oxidizing microorganisms to supply energy to other microorganisms.”
“After sunset, millions of organisms swarm up from the depths to feed on the microorganisms floating in the warm epipelagic zone. Many copepods and invertebrate larvae come up to shallower waters to eat the phytoplankton, which attracts many predators like squid, hatchet fish, and lantern fish. The migration of the many bioluminescent animals is visible to the naked eye. This nightly vertical migration is the largest (in terms of the number of animals) on our planet.”
